The present disclosure relates generally to medical devices and, more particularly, to sensors for determining physiological parameters.
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of medicine, doctors often desire to monitor certain physiological characteristics of their patients. Accordingly, a wide variety of devices have been developed for monitoring certain physiological characteristics of a patient. Such devices provide doctors and other healthcare personnel with the information they need to provide the best possible healthcare for their patients. As a result, such monitoring devices have become an indispensable part of modern medicine. For example, photoplethysmography is a common technique for monitoring physiological characteristics of a patient, and one device based upon photoplethysmography techniques is commonly referred to as a pulse oximeter. Pulse oximeters may be used to measure and monitor various blood flow characteristics of a patient. A pulse oximeter may be utilized to monitor the blood oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsations supplying the tissue, and/or the rate of blood pulsations corresponding to each heartbeat of a patient. In fact, the “pulse” in pulse oximetry refers to the time-varying amount of arterial blood in the tissue during each cardiac cycle.
Pulse oximeters or other photoplethysmography-based devices typically utilize a non-invasive sensor that transmits light through a patient's tissue and that photoelectrically detects the absorption and/or scattering of the transmitted light in such tissue. One or more of the above physiological characteristics may then be calculated based upon the amount of light absorbed or scattered. More specifically, the light passed through the tissue is typically selected to be of one or more wavelengths that may be absorbed or scattered by the blood in an amount correlative to the amount of the blood constituent present in the blood. The amount of light absorbed and/or scattered may then be used to estimate the amount of blood constituent in the tissue using various algorithms.
Pulse oximetry measurement often involves placement of a sensor on a patient's tissue, typically via an adhesive sensor, a clip-style sensor, or a sensor that may be fitted through pressure contact with the tissue. Because these sensors are typically worn for several hours before the sensor is repositioned, pulse oximetry sensors may slightly deform the underlying tissue if the pressure contact is too great. Deformed tissue may lead to reduced measurement accuracy in cases where pressure from the sensor alters the blood flow into the tissue, leading to changes in the pulse oximetry readings. However, inadequate contact with the tissue may result in movement of the sensor relative to the tissue, which may also be associated with measurement inaccuracies.